1. Field of the Invention
This invention relates generally to a meter and amplifier circuit for measuring both current and voltage, and pertains more particularly to a circuit involving two pairs of opposite conductivity transistors having a special circuit configuration associated therewith so that conventional electromechanical indicating devices can be effectively utilized.
2. Description of the Prior Art
Various transistor amplifier circuits have been devised for use in conjunction with electromechanical meters. However, most of the circuits with which I am familiar are quite costly and complicated, frequently requiring careful transistor matching and precision resistors. Also, as far as cost is concerned, battery life has at times been sacrificed in order to make the overall circuit less expensive. Usually, there is an objectionable amount of current drain from the circuit being measured. Even line voltage interference, where step-down transformers and rectifiers are used instead of batteries to supply the low DC source of power, has proved objectionable heretofore in some types of instruments.
Consequently, while some prior art arrangements have certain acceptable attributes, they have the decided disadvantage of possessing one or more shortcomings. Therefore, a generally satisfactory amplifier and meter combination has not yet been devised as far as I am aware.